Method of bonding polypropylene to rubber and the method of making insulated electrical conductors therefrom

ABSTRACT

The method of the invention comprises the steps of providing an electrically conductive metal core, covering the core with a polyolefin insulating layer, heating the insulating layer to a temperature of 400* to 500* F., then applying a suitable adhesive composition to the insulating layer while it is in the temperature range of 400* to 500* F., then applying a second application of the adhesive composition to the polyolefinadhesive covered conductor, and then applying an elastomer sheath to the polyolefin-adhesive covered conductor after the second application of adhesive composition has been applied thereto.

United States Patent Muise 1 June 6, 1972 METHOD OF BONDING [56]References Cited POLYPROPYLENE T0 RUBBER AND UNITED STATES PATENTS THENIETHOD OF MAKING 3,157,564 11/1964 Tucker et a1 161/243 INSULATEDELECTRICAL 3,258,389 6/1966 Coleman et a1... 1 6 1/2 1 s CONDUCTORSTHEREFROM 3,515,616 6/1970 Miyamoto et a] .1 156/330 [72] inventor:Gordon J. Muise, Westboro, Mass. Prim? Examiner john Geolkasian [73]Assignee: United Steel Corporation Assistant Examiner-Lorraine Kendell22 Filed: Nov. 17, 1970 Perm 21 Appl. No.: 90,473 [57] ABSTRACT RelatedApplication Data The method of the invention comprises the steps ofproviding an electncally conductlve metal core, covermg the core with aDlvlslon 0f 301,138, P 1 1959 polyolefin insulating layer, heating theinsulating layer to a temperature of 400 to 500 F then applying asuitable adhesive composition to the insulating layer while it is in thetem- [52] [1.5. CI ..l56/321, 156/322, 156/333, I perature range of 400to 500 F" then applying a Second 161/242 161/243. 161/253 1 17/ 72plication of the adhesive composition to the polyolefin-adhe- I31. Cl.sive covered conductor,- and hen an elastomer [58] Field of Search"156/321, 322, 333, 161/242, sheath to the polyolefimadhesive cveredconductor after the second application of adhesive composition has beenapplied thereto.

2 Claims, No Drawings METHOD OF BONDING POLYPROPYIENE T RUBBER AND THEMETHOD OF MAKING INSULATED ELECTRICAL CONDUCTORS THEREFROM Thisapplication is a division of my copending application, Ser. No. 801,188,filed Sept. 20, 1969 and now US. Pat. No. 3,592,728.

The present invention relates generally to electrical conductors andmore particularly to a method of making an improved insulated electricalconductor having a polyolefin insulating layer such as polypropylene andan elastomer layer such as neoprene bonded to the insulating layer by asuitable adhesive.

' In the manufacture of electrical cable, it is usual practice to coatthe metal conductors comprising the same with a layer of insulatingmaterial. It is desirable that the insulating layer be flexible as wellas possess goodelecttical insulating properties.

One of the substances that is excellent for such use is the polyolefinpolypropylene. In addition to being a flexible electrical insulator,polypropylene is a thermoplastic which presents a surface that isrelatively inert chemically. This latter property, together with itsexcellent electrical insulating properties and flexibility makespolypropylene an outstanding insulation for electrical conductors.However, polypropylene does not have the necessary rugged durability towithstand rough usage such as, for example, that encountered in the useof mining machine cables which must be dragged over rough ground, rocksand other abrasive surfaces in nonnal use. For this reason, it isnecessary to provide a protective sheath, sleeve or jacket of asubstantially abrasive resistance elastomer such as neoprene over thepolypropylene insulation. Prior to my invention, it was extremelydifficult to effect an adhesive bond between the polypropylene and theneoprene or other elastomer jacket since the surface of thepolypropylene insulation was chemically inert and would not efiectivelyaccept a conventional adhesive bonding agent in a conventional manner.

It is, accordingly, the primary object of my invention to provide animproved method for making an insulated electrical conductor whereby anelastomer jacket can be easily and effectively bonded to apolyolefin-insulated electrical conductor.

It is another object of my invention 'to provide an improved method ofbonding an elastomer to a polyolefin material.

It isa more specialized object of my invention to provide an improvedmethod for making an insulated electrical conductor having a polyolefininsulation and an elastomer jacket on the polyolefin insulation and themethod of bonding an elastomer such as neoprene, butyl rubber, naturalrubber, or chlorosulfonated polyethylene to a polyolefin such aspolypropylene, polyethylene or cross-linked polyethylene including thesteps of heating the polyolefin to a near-molten condition (400to 500F.), then applying to the polyolefin while it is at near-moltencondition an adhesive composition consisting of chlorinated rubber,brorninated poly 2,3- dichlorobutadiene-l,3 and at least 1 percent, byweight, based on the weight of the solids in said composition of apoly-C- nitroso aromatic compound, then applying a second application ofsaid adhesive composition to said adhesive-coated polyolefin, and thenapplying the elastomer to the polyolefin after said second applicationof adhesive composition has been applied thereto, said elastomer beingapplied under pressure to bond the elastomer to the polyolefin.

These and other objects will become more apparent after referring to thefollowing description and explanation.

DESCRIPTION OF THE INVENTION preferably 475 to 500 F.

As the polypropylene-coated conductor emerges from the extruder, anadhesive composition, sold under the trade-mark Chemlok 220, andmanufactured by Hughson Chemical Company, Division of Lord Corporationof Erie, Pennsylvania, is applied onto the near-molten polypropyleneinsulation as a spray. Chemlok 220 is available on the commercial marketand is described and claimed in US. Pat. No.3,258,389, dated June 28,1966. The Chemlok 220 adhesive composition consists of chlorinatedrubber, brorninated poly 2,3-dichlorobutadiene-l,3 and atleast 1.percent, by weight, based on the weight of the solids in saidcomposition, of a poly-C-nitroso aromatic compound. When it is desiredto apply the Chemlock 220 as a spray, the adhesive is diluted withxylene and is applied as a fine mist under pneumatic pressure. It willbe noted, however, the manner of application of the adhesive to thepolypropylene is not restricted to spraying. It may be applied by othermethodssuch as by passing the polypropylene insulated conductor througha full strength solution of the adhesive comp ition.

The polypropylene-and-adhesive coated conductor is then passed through awater filled trough .and taken up on a reel. Then thepolypropylene-and-adhesive coated conductor is taken off of the reel andanother application of the adhesive Chemlok 220 is applied thereto.

A protective sheath or jacket of neoprene is then applied to thepolypropylene-and-adhesive coated conductor by extrusion whereby theneoprene is bonded tolthe polypropylene.

It was found that the method of the invention could be used with equallybeneficial results in applying other elastomers such as butyl rubber,natural rubber and chlorosulfonated polyethylene to any of thepolyolefins of the group consisting of polypropylene, polyethylene.

lclaim:

l. A method of bonding one of the group of elastomers consisting ofneoprene, butyl rubber, natural rubber, and chlorosulfonatedpolyethylene to one of the group of polyolefins consisting ofpolypropylene, polyethylene, and cross-linked polyethylene comprisingthe steps of first heating the polyolefin to a temperature ranging from400 to 500 F then applying to said polyolefin, while said polyolefin isat said temperature, an adhesive composition 1 consisting of chlorinatedrubber, brorninated poly 2,3-dichlorobutadiene- 1,3 and at least 1percent, by weight, based on the weight of the solids in saidcomposition, of a poly-C-nitroso aromatic compound, then applying asecond application of said adhesive composition to said polyolefin, andthen applying said elastomer to the adhesive coated polyolefin underpressure to bond said elastomer to said polyolefin.

2. A method of bonding neoprene to polypropylene comprising the steps offirst heating said polypropylene to a temperature ranging from 475 to500 F. then applying to said polypropylene, while said polypropylene isat said temperature, an adhesive composition consisting of chlorinatedrubber, brorninated poly 2,3-dichlorobutadiene-l ,3 and at least 1percent, by weight, based on the weight of the solids in saidcomposition, of a poly-C-nitroso aromatic compound, then applying asecond application of .said adhesive composition to said polypropylene,and thenapplying said neoprene to the adhesive coated polypropyleneunder pressure to bond said neoprene to said polypropylene.

polyethylene, and cross-linked

2. A method of bonding neoprene to polypropylene comprising the steps offirst heating said polypropylene to a temperature ranging from 475* to500* F. then applying to said polypropylene, while said polypropylene isat said temperature, an adhesive composition consisting of chlorinatedrubber, brominated poly 2, 3-dichlorobutadiene-1,3 and at least 1percent, by weight, based on the weight of the solids in saidcomposition, of a poly-C-nitroso aromatic compound, then applying asecond application of said adhesive composition to said polypropylene,and then applying said neoprene to the adhesive coated polypropyleneunder pressure to bond said neoprene to said polypropylene.